1. Field of the Invention
This application relates to a reflector apparatus, in particular a parabolic mirror, with a plastic layer on which a plastic sheet with a metal structure is provided and with a casing consisting of two hollow cylinders which can be arranged inside one another and between which the reflector is held.
2. Description of the Prior Art
Reflectors or transreflectors are used for many applications, in particular for the orientation of radar waves. It is already known to produce reflectors for radar applications where a plastic sheet is coated with a metal, in particular aluminum, the plastic sheet is fixed in an injection moulding die and is then overfed with a plastic layer having the necessary shape, for example a parabolic shape. A parabolic mirror is thus formed which is arranged relative to a radar source by a casing. In many cases, this casing consists of a metal, for example of aluminum. A casing of this type can be produced as a cast casing.
It is also known to fix the parabolic mirror in the cast casing between an outer cylinder and an inner cylinder with a seal inserted in-between. In an outer hollow aluminum cylinder having a peripheral, inwardly orientated flange, a seal is placed against this flange, the reflector is subsequently introduced that is followed by an inner cylinder which presses the reflector and the seal against the flange of the outer cylinder.
It has been found that pronounced deformation of the components may occur owing to the different coefficients of thermal expansion of the casing and the reflector. Owing to this deformation, a precise orientation in the radial direction of the reflector relative to the radar transmitter is no longer ensured. As the centrality of the reflector relative to the transmitter is very important for applications where safety is paramount, it is necessary not only to accommodate production tolerances with a reflector apparatus consisting of reflector and casing but also to accommodate for the differing thermal expansion of the various components.